Fuel metering device

ABSTRACT

A device, for supplying fuel in the correct and desired quantity to an internal combustion engine employing spark ignition, compensates for the variation in volumetric efficiency of the engine with engine speed. The device comprises a fuel injection pump of variable delivery and with independent outlets equal in number to the cylinders of the engine to be supplied. The pump is driven from the engine through drive means of the device which includes mechanicallyoperating means for sensing variations in the engine speed and for adjusting the pump delivery in dependence on the speed. The pump outlets may supply injectors which inject into either the inlet passages or ports of the individual engine cylinders, or directly into the cylinder combustion spaces.

0 United States Patent 1191 1 [11] 3,824,975

Bastow 14 1 Jul 23, 1974 FUEL METERING DEVICE [76] Inventor: Donald Bastow, Nullions Woodlands Pnmary Exammer wllham Freeh End, Meus, near Frome Somerset Attorney, Agent, or Firm-Young and Thompson England [22] Filed: Sept. 5, 1972 [57] ABSTRACT PP 236,259 A device, for supplying fuel in the correct and desired quantity to an internal combustion engine employing 52 1 us. Cl. 123/139 AC, 123/139 AL Spark ignition cmpensates the variatic" 123 40 R 417 /206 metric efficiency of the engine with engine speed. [5 1] .Int. Cl. F02m 39/00 The device comprises a fuel injection pump of [58] Field of Search 417/221, 213, 206, 244; variable delivery and with independent outlets equal 123/140 R, 140.3, 139 AC, 139 AL; 91/497 in number to the cylinders of the engine to be supplied. The pump is driven from the engine through [56] References Cited drive means of the device which includes UNITED STATES PATENTS mechanically-operating means for sensing variations in 2 H5 121 4,1938 the engine speed and for adjusting the pump delivery 240o413 5/1946 in dependence on the speed. 2,646,755 7/1953 The pump outlets may supply injectors which inject 2,667,840 2/1954 into either the inlet passages or ports of the individual 3,146,715 9/1964 engine cylinders, or directly into the cylinder 3,311,100 3/1967 Maddalozzo 417/294 combustion Spaces.

FOREIGN PATENTS OR APPLICATIONS 565,043 10/1944 Great Britain 91/497 12 9 Draw F'gures PATENTEUJUL231974 I 3.824.975

SHEET 1 [IF 5 PAIENTEUJULZMHH V 3,824,975 SHEET 1 BF 5 PATENTED JUL 2 3 74 sum 5 m5 1 FUEL METERING DEVICE vice which will effectively measure the quantity of air being consumed and will supply, either break-up into droplets or preferably vaporise, and mix with the incoming air the required quantity of the liquid fuel. In the normal conditions of operation the range of mixture strength which can readily be ignited lies between about 13 and parts by weight of air to one of fuel, and variation of the power output of an engine is thereto it, usually by a throttle valve. In the vast majority of cases this throttle valve forms part of a carburetter providing the fuel metering device which uses the pressure drop of the incoming air through a venturi to introduce fuel into the air-stream through a variety of metering and atomising devices designed to maintain the required proportions of air and fuel appropriate to the engine and its conditions of operation. Where engines have more than one cylinder it is general practice to use one carburetter to supply all or several of these cylinders, both to even out the flow of air through the carburetter and to reduce the overall cost of the equipment. The outlet from the carburetter to the engine must then consist of an inlet tract with a branch to each cylinder supplied, and failure to achieve complete fuel vaporisation and the different flow characteristics of gases and liquids make it difficult to achieve the same mixture strength in each cylinder. Although this problem of distribution between the branches of the inlet tract feeding the different cylinders can be overcome by providing each cylinder with its own carburetter, the manufacturing variations between carburetters mean that they have to be individually adjusted to provide the desired mixture strength over'the range of operating conditions and such adjustment becomes more difficult, tedious and expensive as the number of cylinders increases. Moreover, passing the air through the venturi results in some pressure loss in the incoming air, which at full throttle opening means that the power which the engine can develop is reduced.

With regulations of increasing severity in being and contemplated controlling exhaust emissions, the precise control of the mixture strength of each individual cylinder is becoming more important. A number of devices have been designed and developed which aim at injecting into each inlet port or cylinder for each operating cycle of the engine a quantity of fuel appropriate to the quantity of air flowing into that cylinder. The invention has for its object to provide a fuel metering device to do this in a simple and accurate manner.

According to the invention a device for supplying fuel in the correct and desired quantity to an internal combustion engine comprises a fuel injection pump of variable delivery and with one or moreindependent outlets equal in number to the number of cylinders of fore achieved by controlling the amount of air admitted l the engine to be supplied, drive means through which the pump can be driven from the engine, and mechanically-operating means for sensing variations in the engine speed and for adjusting the pump delivery in dependence on the engine speed.

The adjustment in accordance with engine speedprovided by the invention compensates for the fact that for any engine, in combination with its air inlet and exhaust outlet systems, the volumetric efficiency at full throttle, i.e. the volume of air induced as a percentage of the swept volume of one engine piston stroke, varies with engine speed. This variation in speed can be measured and recorded in any individual engine or type of en gine, and the compensation provided by the device designed accordingly. The injection pump is desirably of plunger type, and it may comprise ball pistons reciprocable in radial cylinder bores in a rotatable cylinder block connected to the drive means, with the ball pistons running on an external track the eccentricity of which with respect to the rotation axis is variable to adjust the pump delivery.

When the device is fitted to an engine the independent outlets are each led to a corresponding injector of the engine, the function of which is to break the delivery of fuel into the smallest practically possible particles and to inject it either into the inlet passage or port of the engine cylinder with which it is associated, as is preferred, or into the cylinder combustion engine itself. The former arrangement is preferred, firstly because the pressure required to achieve satisfactory atomisation is less than that required to inject against engine cylinder compression pressures, and secondly because there is a possibility of vaporising a greater part of the injected fuel by impingement upon hot port and valve surfaces.

Preferably said mechanically-operating means include or operate on an adjustable cam which modifies the pump delivery to match the variations in air consumption or more correctly in retained combustion air with speed. The means may operate centrifugally, with the balancing of centrifugal force on weights against a spring providing a variation in position with speed of a speed-responsive member.

The device may further comprise means for comparing the effective pressure within an inlet tract of the engine with external atmospheric pressure (hereinafter referred to as ambient pressure) and modifying the pump delivery, either in proportion to the pressure difference or at a slightly greater rate than that at which the pressure difference varies so that the tendency is to have a richer mixture for high throttle openings (high inlet tract pressures) and a weaker mixture for small throttle openings (low inlet tract pressures). The means for comparing such pressures may comprise a diaphragm or bellows one side of which is exposed to ambient pressure and the other side of which is connectable to the inlet tract, with the diaphragm or bellows operating against a spring which may consist only of the natural elasticity of the diaphragm or bellows or of this elasticity supplemented by a spring. Choosing the appropriate spring rate of the supplementary spring is a 3 density of the induced air and thus on the effective pressure in the inlet tract.

The density of the induced air also depends upon the temperature of the air in the inlet tract, and thus the device may further comprise means for sensing that temperature and for modifying the pump delivery accordingly. The arrangement may also be such that the fuel- /air mixture is enriched on full throttle operation, to provide more power, and is weakened on part-throttle operation to provide improved economy.

Means may if desired be included for comparing the ambient pressure with a reference pressure and modifying the fuel injection pump delivery accordingly. This may be achieved by a diaphragm or bellows with opposite sides respectively exposed to the reference pressure and the ambient pressure, thereby compensating for both barometric pressure variations and for pressure variations due to altitude. The reference pressure may be predetermined by providing on one side of the diaphragm or bellows an enclosed volume which can be filled during manufacture at the reference pressure. The movement of this diaphragm or bellows will depend upon the spring rate thereof and any supplementary spring, on the diaphragm or bellows area and on the enclosed reference pressure volume. As there is no requirement for a connection from any remote space to either side of this diaphragm or bellows the latter can with advantage form part of the connection between the first-mentioned diaphragm or bellows and the cam or other means by which the pump delivery is varied.

The device may include a primary fuel supply pump drawing from an internal fuel storage tank and feeding to the suction side of the fuel injection pump, delivering at a pressure sufficient to ensure complete filling of the fuel injection pump cylinders at the maximum speed at which the pump will be required to operate. Means may be. provided to collect leakage from the fuel injection pump and relevant clearances within the device, and for returning the leakage either to the fuel tank or to the suction side of the primary pump when provided. If return to the fuel tank cannot be achieved by gravity a housing of the device may be provided with a sump into which the leakage fuel drains. A float responsive to the fuel level in the sump may operate linkage which at a given upper level operates a valve to permit the primary pump to suck up fuel from the sump and, at a given lower level, changes over that valve so that the primary pump is no longer connected to the sump. If the main fuel tank is to be above the fuel injection pump it is necessary to arrange for the float movement to be effective to cut off the supply from the tank while the sump is connected to the primary pump.

A device in accordance with the invention for supplying fuel to a four-cylinder internal combustion engine will now be described, by way of example, with reference to the accompanying drawings. In the drawings:

FIG. 1 is a vertical cross-sectional view of the device taken through the longitudinal axis of a drive shaft thereof,

FIG. 2 is a detail sectional view taken on the line II II in FIG. 1,

FIG. 3 is a similar view taken on the line Ill III in FIG. 2,

FIG. 4 is a rear end view of the device,

FIG. 5 is a top view of the device with a cover plate removed,

FIG. 6 is a sectional view on the line VI VI in FIG.

FIG. 7 is a part-sectional view on the line VII VII in FIG. 6,

FIG. 8 is a sectional view on the line VIII VIII in FIG. 7, and

FIG. 9 is an underneath view with a sump portion removed and certain internal components not shown.

The device is self-contained with a housing I having a main body portion 2, a rear end cap 3, a top cover plate 4 and a bottom sump portion 5. Drive means comprise a drive shaft 6 which projects through a front end wall of the body portion 2, the shaft being supported at its projecting end in a caged needle roller bearing 7. Two shaft seals 8 are respectively positioned at either side of the bearing 7. The shaft 6 has an outer end taper on which, as shown in FIG. 1, is fitted a sprocket, gearwheel or other coupling member 9 so that it may be driven by the engine in fixed speed and angular relationship thereto.

A fuel injection pump comprises an annular rotatable cylinder block 10 mounted on an inwardly projecting spigot portion 12 of the end cap 3. The block 10, shown more particularly in FIGS. 1 to 3, has four angularly spaced radial cylinder bores 13a, 13b, 13c and 13d in which four spherical ball plunger type pistons 14a, 14b, 14c and 14d respectively operate. The four cylinder bores 13 individually supply the engine cylinders through external pipes 15 (FIG. 4) which deliver to appropriate positions in an inlet tract of the engine (which is not shown), or directly into the engine cylinders, through injectors of known form arranged so that injection does not commence until a predetermined pressure has been reached, this pressure being chosen to ensure acceptably fine atomisation of the injected fuel.

' In all cases the angular spacing of the cylinder bores 13 corresponds to the firing intervals of theengine cylinders to be supplied, and the ball pistons 14 are maintained in contact with a ring abutment in the form of an annular external track 16 which effectively operates as the outer race of an-angular contact ball bearing. This provides offsetting of the points of contact of the ball pistons 14 with the track 16 from the plane containing the axes of the bores 13, and this is preferred as it produces rotation of each ball 14 about an axis not perpendicular to that plane. The effect of centrifugal force produced by ball rotation on the fuel being pumped tends to create two dry spots at the points where the ball rotational axis passes through the ball surface, and it is therefore beneficial if these dry spots are not in contact with the corresponding cylinder bore 13.

The block 10 is fixed by a ring of bolts 17 to an inner end coupling flange 18 of the shaft 6. Reciprocatory movement of the ball pistons 14 in the cylinder bores 13, on rotation of the shaft 6, results from the positioning of the ball track 16 eccentrically with respect to the axis of rotation A A of the shaft 6 and block 10, the stroke of the pistons 14 being twice the eccentricity. Adjusting movement of the track 16 thus provides a ready means of varying the piston stroke and hence controlling the delivery of fuel to each engine cylinder. Drillings in the spigot 12 provide a single fuel feed passage 19, common to all the cylinder bores 13, and separate fuel delivery passages 20a, 20b, x20c and 20d individually associated with the respective cylinder bores 13. These passages are shown more particularly in FIGS. 2 and 3, for clarity the passages being omitted from FIG. 1.

The inlet passage 19 extends from the inner end of the spigot 12 and is connected to a peripheral groove 22 which occupies rather less than half the circumference of the spigot 12, and this groove is angularly positioned so as to be in communication during the outward stroke of each ball piston 14a with a port and radial passage 23a, 23b, 230 or 23d leading to the corresponding cylinder bore 13. The passage 19 is kept filled with fuel by a gear-type primary pump 24, at a pressure sufficient to ensure complete filling of each cylinder bore 13 with fuel on the suction stroke of the corresponding piston 14 at the maximum speed at which the pump is required to run. The primary pump 24 supplies the inlet passage 19 of the injection pump through a supply channel 25 provided by a central blind drilling in the shaft 6 leading from the flange 18.

Each injection pump cylinder bore 13 is also connected to a separate internal port in the block 10 by the corresponding one of four inclined delivery passages 26a, 26b, 26c XI and 26d drilled in the block 10. These passages respectively communicate, over an appropriate angular delivery range, with corresponding ones of four peripheral grooves 27a, 27b, 27c and 27d axially spaced along the spigot 12. These grooves 27 communicate through short radial drillings 28a, 28b, 28c and 28d with the delivery passages 20a, 20b, 20c and 20d already referred to. As shown in FIGS. 2 and 3 the passages 20 communicate through passages 29a, 29b, 29c and 29d, respectively, with external connections on the end cap 3 to which the external pipes 15 already referred to are connected.

The primary supply pump 24 consists of two gears, a driven gear 30 mounted directly on the shaft 6 on serrations and a gear 32 meshing with and driven by the gear 30. The gears 30 and 32 are contained in a recess 33 on the inner side of a front wall of the housing body 2 and they are retained in the recess by an internal cover plate 34. A suction inlet connection 35 leads to a transverse drilling 36 in thehousing, from which a further short drilling 37 leads to the suction side of the pump 24. As shown in FIG. 7 the cover plate 34 has a corresponding transverse drilling 38, with a short drilling 39 which leads to the delivery side of the pump 24 and a further drilling 40 (FIG. 1) leading to a groove 42 in a bore in the cover plate 34 surrounding the shaft 6. A diametral drilling 43 through the shaft provides a connection from the groove 42 to the supply channel 25 in the shaft 6, through which the primary pump 24 delivers to the injection pump inlet passage 19. The outer end of the blind drilling 38 in the cover plate 34 is closed by a plug 44.

It will be appreciated that the gear pump 24 must be proportioned to supply the maximum fuel demand of the engine, and that for much of the time it will therefore be operating with excess delivery. A spring-loaded valve 45 is disposed between the suction inlet drilling 36 in the housing 1 and the primary delivery drilling 38 in the cover plate 34, and this provides a relief valve which handles the surplus delivery of the primary pump 24 and the opening pressure of which controls the primary supply pressure to the injection pump.

Mechanically-operating means which adjust the pump delivery in dependence on the engine speed are also contained within the housing 1. An annular speedresponsive member 46 surrounds and is axially movable on the shaft 6, and it has a concave surface 47 of part-toroidal form which faces a flat radial surface 48 on the adjacent side of the flange 18. A number of balls 49 forming speed-sensing members are disposed between the facing surfaces 47 and 48 which are urged together by a spring 50 acting through a linkage 52. In section the part-toroidal surface 47 is somewhat less than a quarter circle the inner extremity of which is at a small angle, such as 5 or l0, with respect to a plane normal to the rotational axis A A, and the outer extremity of which is at an angle of some 60 or 70 to such normal plane.

The combination of spring load and surface configuration tends to keep the balls 49 at the smallest radius around the shaft 6, but on rotation of the latter the centrifugal force tends to force the balls 49 radially outwardly. This results in separation of the surfaces 47 and 48, and the resultant axial movement of the member 46 is transmitted through the linkage 52 directly to a linear wedge cam 53 on which the spring 50 acts. This arrangement, with the spring 50 acting on the cam 53, avoids inaccuracies due to play in the linkage connections and the pin joints, pivots, etc. are always loaded in the same direction and no lost motion is transmitted.

The cam 53 provides an upper abutment for the ball track 16 which is urged upwardly, into engagement with the cam, by a spring 54. Axial movement of the speed-responsive member 46 results in longitudinal movement of the cam 53 parallel to the axis A A so that the varying thickness of the cam varies the eccentricity of the track 16 and hence the injection pump delivery. By suitable choice of the initial force and the rate of the spring 50 the relationship between rotational shaft speed and axial separation of the surfaces 47 and 48 can be sufficiently close to linear to provide satisfactory control of the injection pump delivery in accordance with the effective air consumption of the engine.

The linkage 52 comprises a bifurcated lever arrangement 55 the limbs of which pivot about an axis at right angles to the axis A A on lugs 56 (FIG. 5) on the pump cover place 34, and a link 57 which at one end is pivotally connected to the lever arrangement 55 and at the other end is pivotally connected to the cam 53. The lever arrangement 55 both reverses and multiplies the axial movement of the member 46 along the shaft 6, and the member 46 acts on inturned bottom ends of the lever arms 55 through a thrust pad 51. The transmission of the spring force to the member 46 tends to make it rotate at a slightly lower speed than the opposing surface on the flange 18. This slight relative rotation of the surfaces 47 and 48 allows the balls 49 to move inwardly and outwardly upon the surfaces by a rolling motion only, thus minimising friction and increasing the sensitivity of the speed-responsive adjustment of the device.

As an alternative, instead of being left free to rotate the member 46 may be held stationary in the rotational sense. The result of doing so, should it be desired, is that the speed of the balls is approximately halved.

The ball track 16 is located axially between guide surfaces 58 on the end cap 3 and guide surfaces 59 in the body portion 2; it is located radially and laterally of the housing 1 in the horizontal direction by opposing flat surfaces 60 in the body portion 2 and the spacing of which only slightly exceeds the external diameter of the track'16. The track is thus movable between these surfaces by the spring 54 to the adjusted eccentric position determined by the position of the cam 53. The top surface of the cam 53 bears against a roller 62 the position of which is the combined result of pressure and temperature-responsive means now to be described.

Means for'comparing the effective pressure within the inlet tract of the engine with the ambient pressure and modifying the injection pump delivery accordingly comprise a bellows 63, see particularly FIG. 6, mounted in the lower part of the housing 1 with the longitudinal axis of the bellows vertical. The bellows 63 is fixed at the upper end to a mounting bracket 64 within the body portion 2, and the interior of the bellows is connected through drillings in the bracket 64 and the body portion 2 to'an external side connection 65. The connection 65 is connected via an external pipe (not 7 shown) either to the common inlet tract of the engine cylinders or, when each engine cylinder has a separate inlet tract, to the inlet tract of one cylinder. Reduction in inlet tract pressure thus contracts the bellows 63 and the movement of the lower end thereof is transmitted by a rod 66 fixed to the lower end and passing through the upper end and a guide bore 67 in the bracket 64. Upward movement of the rod 66 is opposed by a wire spring 61 the intial load and rate of which are chosen, in relation to the cross-sectional area of the bellows and the leverage ratio provided by the linkage between the bellows and the roller 62, to provide the desired variation in pump delivery with inlet tract pressure as compared with ambient pressure.

Means which compensate for variations in ambient pressure comprise a second bellows 68 secured to the rod 66 and effectively forming an extension thereof. It will be appreciated that when such pressure compensation is not required the bellows 68 can be omitted. The bellows 68 is sealed at a predetermined internal reference pressure and expands with reducing ambient pressure, thereby compensating for the reduced movement of the rod 66 in such conditions. If the bellows 68 had no spring rate, i.e. was completely free to expand and contract, the pressure of the contained air would remain equal to the ambient pressure and the axial extension of the bellows 68 with'reduction in atmospheric pressure would depend only on the volume of the bellows and the cross-sectional area thereof. As the bellows 68 cannot be without spring rate, a somewhat larger volume of air needs to be enclosed therein to provide the pressure difference implied by the effective rate at the desired movement for a given difference between the reference and ambient pressures.

In order to measure the temperature in the engine inlet tract a part of the latter is surrounded by an annular chamber (indicated at 69 in FIG. 6) connected by a small bore pipe 70 to a metal bellows 72 of the device contained within the housing 1. The chamber 69, pipe 70 and bellows 72 are filled with a liquid the properties of which, in relation to thermal bulk expansion in relation to its envelope and thermal conductivity, make it suitable to indicate by its change in relative volume the temperature of the chamber 69 and hence, with some delay, that of the air flowing within the engine inlet tract. This delay is theoretically undesirable but is in practical terms acceptable as it is unlikely that very rapid temperature change will normally occur. The relative expansion of the liquid and its envelope is indicated by movement of the upper end of the bellows 72 in relation to the lower end which is fixed to the base of the body portion 2.

The upper end of the bellows 72 is connected to a rod 73 which extends upwardly to a pivotal connection to one end of a generally horizontal lever 74, and this lever carries a pivot 75 for a pressure-responsive lever 76, which reacts to air density variation within the inlet tract pivotally connected to the upper end of a rod 77 which extends upwardly from the bellows 68 and which is guided in a guide block 71 within the bellows 68. The lever 76 carries the roller 62 which bears against the upper surface of the wedge cam 53. Thus, temperature variation control movements are superimposed on the air pressure control movements, and the fulcrum of the temperature control lever 75 is defined by a normally fixed pivot 78 supported by a third lever 79 pivoted at one end within the housing 1 about a permanently fixed axis provided by a pivot 80 projecting inwardly from the body portion 2.

The free end of the lever 79 is formed as a pad 82 engaged by the lower end of an adjusting screw 83 threaded through a boss 84 on the cover plate 4. The screw 83 is locked in position, either by means of a lock nut 81 or a friction device (not illustrated) such as a coil spring lying between the head of the screw 83 and the boss 84, and downward movement of the lever 79 by the screw increases the delivery of the injection pump byadjustment of the position of the pivot 78.

This provides for overall setting-up adjustment when the device is fitted and during engine servicing.

Bearing in mind that the stroke of the ball pistons 14 cannot be expected to exceed 0.3 times the ball diameter, the fuel required for each working cycle of an engine cylinder of 250 cm swept volume can be provided by balls of 5 mm diameter and a stroke of 1.5 mm (0.060 inch), which corresponds to a maximum eccentricity of the ball track 16 of 0.030 inch. To maintain reasonable travel at the pressure-sensitive bellows 63 and 68 a leverage ratio of 9:1 between bellows and track travel has been chosen for the present device, and the pivot 75 about which the pressure-responsive lever 76 operates as a result has to be on the side of the ball plane remote from the bellows. The temperatureresponsive lever 74 has a ratio of 12:], so that the pivot 78 is disposed even further towards the rear end of the housing and beyond the pivot 75.

The sump portion 5, which is attached to the body portion 2 by screws 85, collects fuel leaking from the injection pump and the various clearances within the device. A float 86 lies within the sump portion 5 and is pivoted to the body portion 2 by an arm 87. The float 86 is of generally cylindrical form disposed laterally of the housing 1 and is fixed to the arm 87 at one-end, and the other end of the float is fixed to a lever projection 88 formed with a long slot 89 disposed perpendicular to a radius from the float pivot axis. From the base of the sump portion 5 a passage 90 leads to a passage 92 in the body portion 2. The passage 92 leads, as shown in FIG. 8, to the transverse drilling 36 to which the external fuel tank is connected, and breaks into the drilling 36 on the side of the gear pump inlet drilling 37 remote from the external tank connection 35. A piston valve 93 slidable in the drilling 36 and projecting from the inner end-thereof has a land 94 which normally lies between the passage 92 and the gear pump inlet drilling 37. Beyond the land 94 the valve 93 is of reduced diameter to provide a central spindle portion 95 beyond which the valve 93 provides a further land sealing the end of the drilling 36.

The inner end of the valve 93 is connected at 96 to one apex of a triangular bell-cranklever 97, another apex of which is pivotally mounted at 98 in the body portion 2. The third apex of the lever 97 is pivotally connected at 99 to the upper end of a rod 100 the lower end of which has a pin 102 which fits within the slot 89 in the float lever 88, being retained therein by a washer and retaining device 103. The length of the slot 89 is equal to the length of the travel at that point for the full movement of the float between predetermined upper and lower levels of fuel in the sump portion 5, less the travel necessary to operate the valve 93. An overcentre toggle spring 104 is connected between the body portion 2 and the pivotal connection 99, and this ensures that the lever 97 and hence the valve member 93 are always urged to one or other of their extreme positions and operate with a snap-over action.

As the leakage lever in the sump portion 5 rises, the float 86 rises until the lower end of the slot 89 contacts the pin 102, as shown in FIG. 8. Further leakage and hence rise in float level moves the rod 100 and the lever upwardly to a position where the toggle spring is just beyond the overcentre point, when the piston valve 9 moves over to a position in which the land 94 is disposed between the gear pump inlet drilling 37 and the tank connection 35, as shown in FIG. 7 and in broken lines in FIG. 8. The gear pump suction is thus connected to the passage 92 and the pump sucks up the leakage fuel, the length of the spindle portion 95 of the valve 93 being sufficient to provide the requisite connection to permit this. As the level in the sump drops the float falls until, in a like manner, valve operation in the opposite direction occurs. The piston valve 93 now moves to a position shown in full lines in FIG. 8 in which the land 94 is disposed between the passage 92 and the pump inlet drilling 37, so that the gear pump suction is again connected to the external fuel tank and sealed from the sump.

I claim:

1. A device for supplying liquid fuel in controlled quantity to an internal combustion engine with spark ignition, comprising;

a fuel injection pump having a rotary cylinder block with a cylinder bore, an outlet duct communicating with said bore, a plunger in the bore and a ring abutment providing for reciprocation of the plunger as the cylinder block rotates, the ring abutment being movable to change the throw of the plunger and hence the pump delivery through said outlet duct,

drive means through which the pump can be driven from the engine,

sensing means including a centrifugally-operating device responsive to the speed of the drive means and a sensor producing a movement dependent upon the density of engine inlet-tract air, and

a wedge cam having wedging movement controlled by the air-density sensor,

said wedge cam operating to vary the position of the ring abutment to control the throw of the plunger and hence the pump delivery in dependence on engine speed and air density.

2. A device according to claim 1, wherein the airdensity sensor comprises means for measuring the temperature of engine inlet-tract air.

3. A device according to claim 1, including a lever operated by the air-density sensor, and an abutment on said lever against which the wedge cam rests to define the effective lateral position of the wedge cam.

4. A device according to claim 1, including a primary fuel supply pump to supply said injection pump and with a suction inlet adapted to be connected to a fuel storage tank.

5. A device according to claim 4, wherein means for collecting leakage from said injection pump act to supply the leakage fuel to the suction side of the primary fuel pump.

-6. A device according to claim 5, including a sump in which said leakage collects and means including a float to sense the level of the leakage fuel in the sump and at a predetermined level control a changeover valve at the suction side of the primary fuel pump so that the latter draws fuel from the sump instead of from the fuel storage tank, the valve changing back to the normal position when the level in the sump falls to a predetermined value.

7. A device according to claim 1, wherein the rotary cylinder block has a plurality of cylinder bores, a plunger in each cylinder bore and an outlet duct communicating with each said cylinder bore for fuel delivery to individual cylinders of a multi-cylinder engine.

8. A device according to claim 7, wherein the cylinder bores are radial with ball plungers therein and the ring abutment comprises a ball race surrounding the cylinder block and movable to change the eccentricity.

9. A device according to claim 1, wherein the airdensity sensor comprises means for comparing the effective pressure within an inlet tract of the engine with ambient pressure.

10. A device according to claim 9, wherein the means for comparing said pressures comprises a movable member subject to differential pressure, one side of which is exposed to external pressure, duct means being provided for applying engine inlet-tract air to the other side.

11. A device according to claim 10, including a first lever operated by said movable member subject to differential pressure and operative upon the wedge cam to determine the effective lateral position of the wedge cam, and a second lever to which the first lever is pivoted, the second lever being angularly adjustable.

12. A device according to claim 9, wherein the airdensity sensor includes barometric means for compensating for changes in ambient pressure. 

1. A device for supplying liquid fuel in controlled quantity to an internal combustion engine with spark ignition, comprising; a fuel injection pump having a rotary cylinder block with a cylindEr bore, an outlet duct communicating with said bore, a plunger in the bore and a ring abutment providing for reciprocation of the plunger as the cylinder block rotates, the ring abutment being movable to change the throw of the plunger and hence the pump delivery through said outlet duct, drive means through which the pump can be driven from the engine, sensing means including a centrifugally-operating device responsive to the speed of the drive means and a sensor producing a movement dependent upon the density of engine inlet-tract air, and a wedge cam having wedging movement controlled by the airdensity sensor, said wedge cam operating to vary the position of the ring abutment to control the throw of the plunger and hence the pump delivery in dependence on engine speed and air density.
 2. A device according to claim 1, wherein the air-density sensor comprises means for measuring the temperature of engine inlet-tract air.
 3. A device according to claim 1, including a lever operated by the air-density sensor, and an abutment on said lever against which the wedge cam rests to define the effective lateral position of the wedge cam.
 4. A device according to claim 1, including a primary fuel supply pump to supply said injection pump and with a suction inlet adapted to be connected to a fuel storage tank.
 5. A device according to claim 4, wherein means for collecting leakage from said injection pump act to supply the leakage fuel to the suction side of the primary fuel pump.
 6. A device according to claim 5, including a sump in which said leakage collects and means including a float to sense the level of the leakage fuel in the sump and at a predetermined level control a changeover valve at the suction side of the primary fuel pump so that the latter draws fuel from the sump instead of from the fuel storage tank, the valve changing back to the normal position when the level in the sump falls to a predetermined value.
 7. A device according to claim 1, wherein the rotary cylinder block has a plurality of cylinder bores, a plunger in each cylinder bore and an outlet duct communicating with each said cylinder bore for fuel delivery to individual cylinders of a multi-cylinder engine.
 8. A device according to claim 7, wherein the cylinder bores are radial with ball plungers therein and the ring abutment comprises a ball race surrounding the cylinder block and movable to change the eccentricity.
 9. A device according to claim 1, wherein the air-density sensor comprises means for comparing the effective pressure within an inlet tract of the engine with ambient pressure.
 10. A device according to claim 9, wherein the means for comparing said pressures comprises a movable member subject to differential pressure, one side of which is exposed to external pressure, duct means being provided for applying engine inlet-tract air to the other side.
 11. A device according to claim 10, including a first lever operated by said movable member subject to differential pressure and operative upon the wedge cam to determine the effective lateral position of the wedge cam, and a second lever to which the first lever is pivoted, the second lever being angularly adjustable.
 12. A device according to claim 9, wherein the air-density sensor includes barometric means for compensating for changes in ambient pressure. 